Posted by Karla on Monday, August 29, 2011 at 5:37am.
Hey :)
I was wondering if someone could tell me if this answer and working is correct or not...
Cos theta =0.25
Cos inverse 0.25 = 14
therefore theta equals:
18014=194or/and
180+14=166
Any help would be much appreciated :)
Thanks!

Maths  Jai, Monday, August 29, 2011 at 6:10am
cos (theta) = 0.25
theta = cos^1 (0.25)
there are two answers:
theta = 104.48 degrees = 3.65 radians
and,
theta = 104.48 degrees = 3.65 radians
hope this helps~ :)

Maths  Reiny, Monday, August 29, 2011 at 8:30am
Usually the required angles are in the domain of
0 ≤ Ø ≤ 360°
Since the given cosØ is negative, by the CAST rule,
Ø must be in either quadrant II or III
from cosØ = +.25 we get the reference angle of 75.52°
so Ø = 180°75.52° or 104.48° (Jai's answer)
or Ø = 180°+75.52° or 255.52°
Since the period of cosØ is 360°, you can get other answers by adding or subtracting multiples of 360°
(For Jai's second answer, 255.52  360° = 104.48°)
I have no idea how you came up with
inverse cos (.25) = 14
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